The present technology relates to a semiconductor device and a manufacturing method thereof, and more particularly to a technology field of a semiconductor device in which a predetermined metal layer is disposed between a pad electrode and a solder bump.
For example, as known as a flip chip method and the like, an IC chip (semiconductor chip) is bonded (mounted) onto the mounting substrate including a semiconductor substrate through a solder bump. In the semiconductor device in which a semiconductor chip is mounted on the mounting substrate through the solder bump, an under-bump metal (hereinafter, referred to as “UBM”) is disposed between a pad electrode and a solder bump (for example, refer to Japanese Unexamined Patent Application Publication No. 2008-28112 and Japanese Unexamined Patent Application Publication No. 2012-80043). The UBM is provided so as to improve a degree of bonding adhesion between the pad electrode (for example, Al-based material) and the solder bump.
A formation of the UBM is performed, for example, as follows. That is, first, a metal seed layer (underlying metal layer: for example, Cu, Ti, and the like) which is in contact with the pad electrode is formed. A formation of the metal seed layer is performed by PVD (physical vapor deposition) and CVD (chemical vapor deposition) over an entire surface of a wafer in terms of ensuring reliability and the like. Then, a main metal layer made of, for example, Ni and the like is formed on the metal seed layer by electrolytic plating in which the metal seed layer is used as an electrode. The electrolytic plating is performed after a mask which has an opening only at a position corresponding to the pad electrode is processed, and accordingly, the main metal layer is formed to have a predetermined diameter.
The main metal layer formed to have a predetermined diameter as described above and a metal seed layer formed on the underlying side thereof function as the UBM.
Here, the metal seed layer formed on the entire surface of a wafer as described above being left as it is, results in the pad electrodes being electrically connected to each other. Therefore, the metal seed layer is used during the above-mentioned electrolytic plating, and then eventually removes (removes the main metal layer regarded as a mask) a portion protruding from the main metal layer by etching and the like. Etching at this time is performed using isotropic etching such as wet etching and the like.